Failure when saving in satellite-native projection

[pnuu]

Describe the bug Processing fails when using satellite-native projection, that is null as projection in trollflow.yaml.

To Reproduce Use null as area, like in the following stripped-down non-working product list:

product_list:
  areas:
    null:
      areaname: geos
      products:
        airmass:
          productname: airmass

Expected behavior The images should be saved without resampling.

Actual results Process crashes with

Traceback (most recent call last):
  File "/home/users/satman/current/lib/python3.8/multiprocessing/process.py", line 315, in _bootstrap
    self.run()
  File "/home/users/satman/current/lib/python3.8/multiprocessing/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
  File "/home/users/satman/current/lib/python3.8/site-packages/trollflow2/launcher.py", line 268, in process
    cwrk.pop('fun')(job, **cwrk)
  File "/home/users/satman/current/lib/python3.8/site-packages/trollflow2/plugins/__init__.py", line 136, in resample
    if not set(scn.datasets.keys()).issuperset(scn.wishlist):
AttributeError: 'Scene' object has no attribute 'datasets'

Environment Info:

• Trollflow2 Version: 0.7.2.dev19+g4158921 (latest master)
• Satpy Version: 0.23.0

[djhoese]

@mraspaud made .datasets private now so it is ._datasets, but you should be able to do scn.keys() instead anyway.